1. Field of the Invention
The present invention relates to a semiconductor device and a method for producing the same, more particularly to a semiconductor device in which both optical semiconductor elements and ordinary electronic semiconductor elements are substantially flatly formed on a single substrate.
2. Description of the Related Art
Recent advances in the technologies of crystal growth and device production have make it possible to combine optical and electronic devices into a single chip. Such an optoelectronic integrated circuit (OEIC) is not only smaller and easier to use in various systems but also speedier, more reliable, and less noisy than hybridized discrete devices. A particularly attractive and important OEIC is one wherein an optical semiconductor element, for example, a laser diode (LD) or photo diode (PD), is monolithically integrated with a field effect transistor (FET) driver.
In fabricating a laser/FET unit or PD/FET unit, there is a problem in how to match the laser structure to the FET structure, as each component has a very different layer structure. A laser has a higher structure than FET's. As conventional photolithographic technology requires a wafer with an even surface, the laser must therefore be formed in an etched groove. Assuming the substrate is one of (100) oriented semiinsulating GaAs substrate, when the substrate is chemically etched, a (011) face is exposed as a side wall, the (011) face forms a 55.degree. angle with respect to the (100) top surface so that a groove having a sharp step is formed. This sharp step itself, however, makes application of the photolithographic technology difficult. Thus, high integration of the laser/FET unit becomes difficult.
Further, the sharp 55.degree. angle step often results in breakage of wiring and thus a reduced production yield.